1. Field of the Invention:
This invention relates to a tube puller for removing heat exchanger tubes from a tubesheet of a steam generator and more particularly to such apparatus for removing, during one pulling stroke, a plurality of such tubes.
2. Description of the Prior Art:
Hydraulically operated tube pulling apparatus for removing heat exchanger tubes from a heat exchanger such as a steam generator are known. Typically, such apparatus includes a tube gripping member, disposed within the end of the tube to be removed and expanded into gripping engagement with the interior surface of the tube. The gripping member is connected to an operating rod of a hydraulic cylinder that pulls the tube from the tubesheet in which it is mounted.
The expandable gripping member typically includes an externally toothed tube capable of being expanded into engagement with the inner surface of the heat exchanger tube by an axially tapered rod which, upon being moved axially within the gripping member, expands the gripping tube into a proper gripping engagement. Such tube pulling apparatus can be made to operate quite well, especially when a proper gripping relationship is established between the gripping surface of the expandable member and the inner surface of the heat exchanger tube. One factor in establishing this proper relationship is the radially expanding force provided by the internal tapered rod which expands the gripping member. Thus, for any one tube to be removed, the tapered rod must be positioned axially to a point resulting in such expanding force and gripping relationship being established.
In removing the tubes (or tube stubs) of a nuclear steam generator, it is preferable to increase the speed of the tube removal process (and thus reduce the personnel exposure to the irradiated equipment) by having tube pulling apparatus capable of removing a plurality of tubes upon each retraction of the hydraulic pulling cylinder. However, as the final axial position of each tapered rod for expanding the expandable tube into the proper or effective gripping relationship within the associated stub tube, can vary for each tube stub to be removed, a single automatic member which positions a plurality of such tapered rods must permit each individual tapered rod to attain the proper axial position without altering or affecting the ability of each of the other tapered rods in the group to achieve an axial position for establishing a like gripping engagement for each of the other tubes.